1. Field of the Intention
The invention relates to a Crypto-engine for authentication and information data scrambling.
2. Description of Prior Art
The security of many cryptographic systems depends upon the generation of unpredictable quantities that must be of sufficient size and random. Linear feedback shift registers (LFSRs), due to their simplicity and efficiency of implementation, are the basic building blocks in most popular used stream cipher generators. However, some attractive properties associated with LFSRs give rise to the failure of many of these constructions to meet a good cryptographic strength. In particular, the inherent linearity of LFSRs and the algebraic structure are frequently the basis for breaking these cryptographic systems. The generating polynomial can easily be derived and the initial states that generate a specific sequence will produce a number of predictable sequences. To avoid this linearity problem, a nonlinear filtering function, whose inputs are taken from some shift register stages to produce an output, is used to destroy the linearity and algebraic structure of the original sequence. The non-linear filter in the form of nonlinear combination generator is essential to make the outcomes more secure. However, most of these filters are designed based on a nonlinear combining function f of the outputs of several LFSRs in parallel. The nonlinear function f employed is a fixed function. Therefore, the mapping defined by the nonlinear function f is a one-to-one mapping, and for the same input imposed on f, the same output will be obtained. Such a generator suffers a divide-and-conquer attack if a correlation exists between the keystream and the output sequences of individual sub-generators. One solution could be to use the Data Encryption Standard (DES) to randomize the output but this is not economical as a substantial amount of hardware is required. Generally stated, problems arise because the stream ciphers or random number generators based on LFSRs are cryptographically unsafe and a substantial amount of hardware has to be used to make it safe.